Only supports base unlit material parameters with the addition of : analytical lights with a diffuse lambert BSDF, interpolated geometric normal and double sided option.
-Make the AO and SO path clean since we're forward based (no more double occlusion and occlusion on emissive).
-Configurable per-lobe specular occlusion on environment lights and debug options. Also use GTAOMultiBounce tint in the context of vertical layering.
(Enabling SO is orthogonal to bentnormals presence, the choosen algo for the data-based occlusion will use the normal or bentnormal if present)
-Bentnormal map which piggy backs on all normal map parameters (add UI code to allow this too)
-Fix GGX energy compensation term application
-Reuse some Lit shader_feature keywords
-SpecularColor mode now selectable
-Dual specular lobe has two parametrization: direct and hazy gloss (Barla et al. 2018-07)
-UI changes to support multiple parametrizations and also avoid useless keyword switching in some instances
-Additional note on specular occlusion and anisotropy